A permanent magnet synchronous motor with a permanent magnet incorporated therein is used as a driving motor mounted on a hybrid vehicle, an electric vehicle and the like. In some cases, the temperature of the permanent magnet becomes higher or lower than a reference temperature (for example, a designed temperature) of the permanent magnet with drive conditions or use environments of the motor.
In this way, when the temperature of the permanent magnet deviates from the reference temperature, there is a possibility of causing various problems.
For example, when the temperature of the permanent magnets is extremely high, the permanent magnet may cause an irreversible demagnetization. Also, when the temperature of the permanent magnet is extremely high or low, the torque may not fall within a predetermined range in some cases.
For this reason, it is necessary to acquire the temperature of the permanent magnet incorporated in the motor and to drive and control the motor on the basis of the temperature of the acquired permanent magnet. However, in general, since the permanent magnet of the permanent magnet synchronous motor is provided on the rotor, it is difficult to directly detect the temperature. Therefore, it has been considered to estimate the temperature of the permanent magnets incorporated in the motor. For example, PTL 1 discloses an invention for estimating the temperature of a permanent magnet in a 3-phase 3-wire type motor using fundamental waves and harmonics such as current or voltage.
Incidentally, the motor described in PTL 1 cannot independently control each phase due to wiring. In contrast, there is an advantage of being able to independently control each phase in a 3-phase 6-wire type motor (generally, an n-phase 2n-wire type motor, n is an integer of 2 or more), and the utilization range has expanded in recent years.